Re: [PATCH 1/2] xfs: move the xfs_can_free_eofblocks call under the IOLOCK

["Darrick J. Wong" <djwong@kernel.org>]

On Fri, Mar 19, 2021 at 05:53:40AM +0000, Christoph Hellwig wrote:
> On Thu, Mar 18, 2021 at 03:33:32PM -0700, Darrick J. Wong wrote:
> > From: Darrick J. Wong <djwong@kernel.org>
> > 
> > In xfs_inode_free_eofblocks, move the xfs_can_free_eofblocks call
> > further down in the function to the point where we have taken the
> > IOLOCK.  This is preparation for the next patch, where we will need that
> > lock (or equivalent) so that we can check if there are any post-eof
> > blocks to clean out.
> > 
> > Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> > ---
> >  fs/xfs/xfs_icache.c |   12 ++++--------
> >  1 file changed, 4 insertions(+), 8 deletions(-)
> > 
> > 
> > diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
> > index e6a62f765422..7353c9fe05db 100644
> > --- a/fs/xfs/xfs_icache.c
> > +++ b/fs/xfs/xfs_icache.c
> > @@ -1294,13 +1294,6 @@ xfs_inode_free_eofblocks(
> >  	if (!xfs_iflags_test(ip, XFS_IEOFBLOCKS))
> >  		return 0;
> >  
> > -	if (!xfs_can_free_eofblocks(ip, false)) {
> > -		/* inode could be preallocated or append-only */
> > -		trace_xfs_inode_free_eofblocks_invalid(ip);
> > -		xfs_inode_clear_eofblocks_tag(ip);
> > -		return 0;
> > -	}
> > -
> >  	/*
> >  	 * If the mapping is dirty the operation can block and wait for some
> >  	 * time. Unless we are waiting, skip it.
> > @@ -1322,7 +1315,10 @@ xfs_inode_free_eofblocks(
> >  	}
> >  	*lockflags |= XFS_IOLOCK_EXCL;
> >  
> > -	return xfs_free_eofblocks(ip);
> > +	if (xfs_can_free_eofblocks(ip, false))
> > +		return xfs_free_eofblocks(ip);
> 
> Don't we still need to clear the radix tree tag here?

I don't think so, because xfs_free_eofblocks will call
xfs_inode_clear_eofblocks_tag if it succeeds in freeing anything.

Though perhaps you're correct that we need to clear the tag if
!xfs_can_free_eofblocks, since we could have been called if
XFS_ICI_BLOCKGC_TAG was set in the radix tree because we once had a
posteof block but now we really only have cow blocks.

Yeah, ok, I'll add that back...

> Also the fs_inode_free_eofblocks_inval tracepoint is unused now.

...along with the tracepoint.

--D